The present invention relates to a process for the treatment or pretreatment of containers made of aluminium, aluminium-containing alloys, magnesium-containing alloys, iron-containing materials such as steel, coated iron-containing materials such as galvanized steel, galvanized metallic materials or metallic materials coated with aluminium or aluminium alloys, tinplate, brass or bronze. These containers may be bags, tubs and similar packagings, bottles, cans, canisters, casks and tubes, such as for example screw-cap closures.
Normally containers are prepared for lacquering in continuous pretreatment units. Such containers, in particular cans, are produced on an industrial scale using foils, metal sheeting or moulded articles made of aluminium, aluminium alloys or tinplate, and after cleaning, pretreatment, lacquering and drying, are filled with beverages, foodstuffs or other products and are then closed and/or sealed. Cans are pretreated in most can pretreatment units at a rate ranging from 500 to 5000 cans per minute. For this reason stringent demands are placed on the speed of all procedures and on the reliable accomplishment of all process steps. Furthermore stringent demands are placed on the sliding properties of the containers in the continuous pretreatment unit, including printer and/or lacquering unit, as well as on the adhesion of lacquer and/or other subsequent coatings and on corrosion resistance.
EP-A-0 293 820, EP-A-0 413 328 and EP-A-0 542 378 describe processes for the coating of aluminium cans with a lubricant that essentially consists of ethoxylated compounds, in particular surfactants.
From WO 98/29580 a process is known for the coating with self-organising molecules for the pretreatment of metallic surfaces. The PCT applications relating to a cerium sulfamate coating process and to a bismuth-accelerated cerium coating process, which were filed round about 19.03.2001 by the Commonwealth Scientific and Industrial Research Organisation of Australia under the title “Process and solution for providing a conversion coating on a metallic surface I” and “Process and solution for providing a conversion coating on a metallic surface II”, describe environmentally friendly, chromium-free coating processes for metallic surfaces. In addition WO 00/63303, WO 00/46312, WO 00/46311, WO 00/46310, WO 00/39356, WO 00/39177, WO 99/14399, WO 98/30735, WO 98/19798, WO 95/24517 and U.S. Pat. No. 6,162,547 describe the coating of metallic surfaces with silane-containing solutions and/or dispersions. These publications are understood to be expressly incorporated in the present application as regards the compositions, process parameters and process steps cited in the above publications. These publications do not disclose however the sliding properties of the coatings described therein and whether this process is also suitable for coating containers, in particular at very high rates and correspondingly short process times. In fact, the coating conditions applicable to individual parts or metal sheeting, in particular in the case of slow coating or in the laboratory, differ markedly from the conditions of the extremely quick conveyor belt operation.